North Atlantic intermediate-water temperature variations based on ostracod Mg/Ca ratios from Ocean Drilling Program (ODP) Hole 1055B document a series of multi-centennial-scale abrupt warming events throughout the last deglaciation and Holocene (up to ∼3 °C). These events are coherent with abrupt climate reversals including Heinrich event 1, the Younger Dryas–Intra-Allerød cold period, and Holocene North Atlantic Deep Water (NADW) reduction periods. Deglacial–Holocene warm events were likely related to reduction in the strength of the upper NADW (Labrador Sea Water). We also found a long-term cooling trend in the ODP 1055 Mg/Ca record indicating continuous Labrador Sea Water strengthening throughout the Holocene. Our results help to better understand deglacial–Holocene upper NADW dynamics that remain poorly understood but can be important for regional and global climates.